Re: [PATCH v9 06/19] x86: Add early SHA-1 support for Secure Launch early measurements
From: ross . philipson
Date: Tue Jun 04 2024 - 17:03:47 EST
On 6/4/24 11:52 AM, Jarkko Sakkinen wrote:
On Fri May 31, 2024 at 4:03 AM EEST, Ross Philipson wrote:
From: "Daniel P. Smith" <dpsmith@xxxxxxxxxxxxxxxxxxxx>
For better or worse, Secure Launch needs SHA-1 and SHA-256. The
choice of hashes used lie with the platform firmware, not with
software, and is often outside of the users control.
Even if we'd prefer to use SHA-256-only, if firmware elected to start us
with the SHA-1 and SHA-256 backs active, we still need SHA-1 to parse
the TPM event log thus far, and deliberately cap the SHA-1 PCRs in order
to safely use SHA-256 for everything else.
The SHA-1 code here has its origins in the code from the main kernel:
commit c4d5b9ffa31f ("crypto: sha1 - implement base layer for SHA-1")
A modified version of this code was introduced to the lib/crypto/sha1.c
to bring it in line with the SHA-256 code and allow it to be pulled into the
setup kernel in the same manner as SHA-256 is.
Signed-off-by: Daniel P. Smith <dpsmith@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Ross Philipson <ross.philipson@xxxxxxxxxx>
---
arch/x86/boot/compressed/Makefile | 2 +
arch/x86/boot/compressed/early_sha1.c | 12 ++++
include/crypto/sha1.h | 1 +
lib/crypto/sha1.c | 81 +++++++++++++++++++++++++++
4 files changed, 96 insertions(+)
create mode 100644 arch/x86/boot/compressed/early_sha1.c
diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index e9522c6893be..3307ebef4e1b 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -118,6 +118,8 @@ vmlinux-objs-$(CONFIG_EFI) += $(obj)/efi.o
vmlinux-objs-$(CONFIG_EFI_MIXED) += $(obj)/efi_mixed.o
vmlinux-objs-$(CONFIG_EFI_STUB) += $(objtree)/drivers/firmware/efi/libstub/lib.a
+vmlinux-objs-$(CONFIG_SECURE_LAUNCH) += $(obj)/early_sha1.o
+
$(obj)/vmlinux: $(vmlinux-objs-y) FORCE
$(call if_changed,ld)
diff --git a/arch/x86/boot/compressed/early_sha1.c b/arch/x86/boot/compressed/early_sha1.c
new file mode 100644
index 000000000000..8a9b904a73ab
--- /dev/null
+++ b/arch/x86/boot/compressed/early_sha1.c
@@ -0,0 +1,12 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2024 Apertus Solutions, LLC.
+ */
+
+#include <linux/init.h>
+#include <linux/linkage.h>
+#include <linux/string.h>
+#include <asm/boot.h>
+#include <asm/unaligned.h>
+
+#include "../../../../lib/crypto/sha1.c"
}
Yep, make sense. Thinking only that should this be just sha1.c.
Comparing this to mainly drivers/firmware/efi/tpm.c, which is not
early_tpm.c where the early actually probably would make more sense
than here. Here sha1 primitive is just needed.
This is definitely a nitpick but why carry a prefix that is not
that useful, right?
I am not 100% sure what you mean here, sorry. Could you clarify about
the prefix? Do you mean why did we choose early_*? There was precedent
for doing that like early_serial_console.c.
diff --git a/include/crypto/sha1.h b/include/crypto/sha1.h
index 044ecea60ac8..d715dd5332e1 100644
--- a/include/crypto/sha1.h
+++ b/include/crypto/sha1.h
@@ -42,5 +42,6 @@ extern int crypto_sha1_finup(struct shash_desc *desc, const u8 *data,
#define SHA1_WORKSPACE_WORDS 16
void sha1_init(__u32 *buf);
void sha1_transform(__u32 *digest, const char *data, __u32 *W);
+void sha1(const u8 *data, unsigned int len, u8 *out);
#endif /* _CRYPTO_SHA1_H */
diff --git a/lib/crypto/sha1.c b/lib/crypto/sha1.c
index 1aebe7be9401..10152125b338 100644
--- a/lib/crypto/sha1.c
+++ b/lib/crypto/sha1.c
@@ -137,4 +137,85 @@ void sha1_init(__u32 *buf)
}
EXPORT_SYMBOL(sha1_init);
+static void __sha1_transform(u32 *digest, const char *data)
+{
+ u32 ws[SHA1_WORKSPACE_WORDS];
+
+ sha1_transform(digest, data, ws);
+
+ memzero_explicit(ws, sizeof(ws));
For the sake of future reference I'd carry always some inline comment
with any memzero_explicit() call site.
We can do that.
+}
+
+static void sha1_update(struct sha1_state *sctx, const u8 *data, unsigned int len)
+{
+ unsigned int partial = sctx->count % SHA1_BLOCK_SIZE;
+
+ sctx->count += len;
+
+ if (likely((partial + len) >= SHA1_BLOCK_SIZE)) {
if (unlikely((partial + len) < SHA1_BLOCK_SIZE))
goto out;
?
We could do it that way. I guess it would cut down in indenting. I defer
to Daniel Smith on this...
+ int blocks;
+
+ if (partial) {
+ int p = SHA1_BLOCK_SIZE - partial;
+
+ memcpy(sctx->buffer + partial, data, p);
+ data += p;
+ len -= p;
+
+ __sha1_transform(sctx->state, sctx->buffer);
+ }
+
+ blocks = len / SHA1_BLOCK_SIZE;
+ len %= SHA1_BLOCK_SIZE;
+
+ if (blocks) {
+ while (blocks--) {
+ __sha1_transform(sctx->state, data);
+ data += SHA1_BLOCK_SIZE;
+ }
+ }
+ partial = 0;
+ }
+
out:
+ if (len)
+ memcpy(sctx->buffer + partial, data, len);
Why not just memcpy() unconditionally?
... and this.
+}
+
+static void sha1_final(struct sha1_state *sctx, u8 *out)
+{
+ const int bit_offset = SHA1_BLOCK_SIZE - sizeof(__be64);
+ unsigned int partial = sctx->count % SHA1_BLOCK_SIZE;
+ __be64 *bits = (__be64 *)(sctx->buffer + bit_offset);
+ __be32 *digest = (__be32 *)out;
+ int i;
+
+ sctx->buffer[partial++] = 0x80;
+ if (partial > bit_offset) {
+ memset(sctx->buffer + partial, 0x0, SHA1_BLOCK_SIZE - partial);
+ partial = 0;
+
+ __sha1_transform(sctx->state, sctx->buffer);
+ }
+
+ memset(sctx->buffer + partial, 0x0, bit_offset - partial);
+ *bits = cpu_to_be64(sctx->count << 3);
+ __sha1_transform(sctx->state, sctx->buffer);
+
+ for (i = 0; i < SHA1_DIGEST_SIZE / sizeof(__be32); i++)
+ put_unaligned_be32(sctx->state[i], digest++);
+
+ *sctx = (struct sha1_state){};
+}
+
+void sha1(const u8 *data, unsigned int len, u8 *out)
+{
+ struct sha1_state sctx = {0};
+
+ sha1_init(sctx.state);
+ sctx.count = 0;
Hmm... so shouldn't C99 take care of this given the initialization
above? I'm not 100% sure here. I.e. given "= {0}", shouldn't this
already be zero?
Yes it seems so. We will look at changing that.
+ sha1_update(&sctx, data, len);
+ sha1_final(&sctx, out);
+}
+EXPORT_SYMBOL(sha1);
+
MODULE_LICENSE("GPL");
BR, Jarkko
Thanks
Ross